sun.misc
Class FpUtils

java.lang.Object
  sun.misc.FpUtils

public class FpUtils
extends Object

The class FpUtils contains static utility methods for manipulating and inspecting float and double floating-point numbers. These methods include functionality recommended or required by the IEEE 754 floating-point standard.

Method Summary

static double	copySign(double magnitude, double sign) Returns the first floating-point argument with the sign of the second floating-point argument.
static float	copySign(float magnitude, float sign) Returns the first floating-point argument with the sign of the second floating-point argument.
static int	getExponent(double d) Returns unbiased exponent of a double.
static int	getExponent(float f) Returns unbiased exponent of a float.
static int	ilogb(double d) Returns unbiased exponent of a double; for subnormal values, the number is treated as if it were normalized.
static int	ilogb(float f) Returns unbiased exponent of a float; for subnormal values, the number is treated as if it were normalized.
static boolean	isFinite(double d) Returns true if the argument is a finite floating-point value; returns false otherwise (for NaN and infinity arguments).
static boolean	isFinite(float f) Returns true if the argument is a finite floating-point value; returns false otherwise (for NaN and infinity arguments).
static boolean	isInfinite(double d) Returns true if the specified number is infinitely large in magnitude, false otherwise.
static boolean	isInfinite(float f) Returns true if the specified number is infinitely large in magnitude, false otherwise.
static boolean	isNaN(double d) Returns true if the specified number is a Not-a-Number (NaN) value, false otherwise.
static boolean	isNaN(float f) Returns true if the specified number is a Not-a-Number (NaN) value, false otherwise.
static boolean	isUnordered(double arg1, double arg2) Returns true if the unordered relation holds between the two arguments.
static boolean	isUnordered(float arg1, float arg2) Returns true if the unordered relation holds between the two arguments.
static double	nextAfter(double start, double direction) Returns the floating-point number adjacent to the first argument in the direction of the second argument.
static float	nextAfter(float start, double direction) Returns the floating-point number adjacent to the first argument in the direction of the second argument.
static double	nextDown(double d) Returns the floating-point value adjacent to d in the direction of negative infinity.
static double	nextDown(float f) Returns the floating-point value adjacent to f in the direction of negative infinity.
static double	nextUp(double d) Returns the floating-point value adjacent to d in the direction of positive infinity.
static float	nextUp(float f) Returns the floating-point value adjacent to f in the direction of positive infinity.
static double	rawCopySign(double magnitude, double sign) Returns the first floating-point argument with the sign of the second floating-point argument.
static float	rawCopySign(float magnitude, float sign) Returns the first floating-point argument with the sign of the second floating-point argument.
static double	scalb(double d, int scale_factor) Return d × 2scale_factor rounded as if performed by a single correctly rounded floating-point multiply to a member of the double value set.
static float	scalb(float f, int scale_factor) Return f × 2scale_factor rounded as if performed by a single correctly rounded floating-point multiply to a member of the float value set.
static double	signum(double d) Returns the signum function of the argument; zero if the argument is zero, 1.0 if the argument is greater than zero, -1.0 if the argument is less than zero.
static float	signum(float f) Returns the signum function of the argument; zero if the argument is zero, 1.0f if the argument is greater than zero, -1.0f if the argument is less than zero.
static double	ulp(double d) Returns the size of an ulp of the argument.
static float	ulp(float f) Returns the size of an ulp of the argument.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Detail

getExponent

public static int getExponent(double d)

Returns unbiased exponent of a double.

getExponent

public static int getExponent(float f)

Returns unbiased exponent of a float.

rawCopySign

public static double rawCopySign(double magnitude,
                                 double sign)

Returns the first floating-point argument with the sign of the second floating-point argument. Note that unlike the copySign method, this method does not require NaN sign arguments to be treated as positive values; implementations are permitted to treat some NaN arguments as positive and other NaN arguments as negative to allow greater performance.

Parameters:

magnitude - the parameter providing the magnitude of the result

sign - the parameter providing the sign of the result

Returns:

a value with the magnitude of magnitude and the sign of sign.

rawCopySign

public static float rawCopySign(float magnitude,
                                float sign)

Returns the first floating-point argument with the sign of the second floating-point argument. Note that unlike the copySign method, this method does not require NaN sign arguments to be treated as positive values; implementations are permitted to treat some NaN arguments as positive and other NaN arguments as negative to allow greater performance.

Parameters:

magnitude - the parameter providing the magnitude of the result

sign - the parameter providing the sign of the result

Returns:

a value with the magnitude of magnitude and the sign of sign.

isFinite

public static boolean isFinite(double d)

Returns true if the argument is a finite floating-point value; returns false otherwise (for NaN and infinity arguments).

Parameters:

d - the double value to be tested

Returns:

true if the argument is a finite floating-point value, false otherwise.

isFinite

public static boolean isFinite(float f)

Returns true if the argument is a finite floating-point value; returns false otherwise (for NaN and infinity arguments).

Parameters:

f - the float value to be tested

Returns:

true if the argument is a finite floating-point value, false otherwise.

isInfinite

public static boolean isInfinite(double d)

Returns true if the specified number is infinitely large in magnitude, false otherwise.

Note that this method is equivalent to the Double.isInfinite method; the functionality is included in this class for convenience.

Parameters:

d - the value to be tested.

Returns:

true if the value of the argument is positive infinity or negative infinity; false otherwise.

isInfinite

public static boolean isInfinite(float f)

Returns true if the specified number is infinitely large in magnitude, false otherwise.

Note that this method is equivalent to the Float.isInfinite method; the functionality is included in this class for convenience.

Parameters:

f - the value to be tested.

Returns:

true if the argument is positive infinity or negative infinity; false otherwise.

isNaN

public static boolean isNaN(double d)

Returns true if the specified number is a Not-a-Number (NaN) value, false otherwise.

Note that this method is equivalent to the Double.isNaN method; the functionality is included in this class for convenience.

Parameters:

d - the value to be tested.

Returns:

true if the value of the argument is NaN; false otherwise.

isNaN

public static boolean isNaN(float f)

Returns true if the specified number is a Not-a-Number (NaN) value, false otherwise.

Note that this method is equivalent to the Float.isNaN method; the functionality is included in this class for convenience.

Parameters:

f - the value to be tested.

Returns:

true if the argument is NaN; false otherwise.

isUnordered

public static boolean isUnordered(double arg1,
                                  double arg2)

Returns true if the unordered relation holds between the two arguments. When two floating-point values are unordered, one value is neither less than, equal to, nor greater than the other. For the unordered relation to be true, at least one argument must be a NaN.

Parameters:

arg1 - the first argument

arg2 - the second argument

Returns:

true if at least one argument is a NaN, false otherwise.

isUnordered

public static boolean isUnordered(float arg1,
                                  float arg2)

Returns true if the unordered relation holds between the two arguments. When two floating-point values are unordered, one value is neither less than, equal to, nor greater than the other. For the unordered relation to be true, at least one argument must be a NaN.

Parameters:

arg1 - the first argument

arg2 - the second argument

Returns:

true if at least one argument is a NaN, false otherwise.

ilogb

public static int ilogb(double d)

Returns unbiased exponent of a double; for subnormal values, the number is treated as if it were normalized. That is for all finite, non-zero, positive numbers x, scalb(x, -ilogb(x)) is always in the range [1, 2).

Special cases:

• If the argument is NaN, then the result is 2³⁰.
• If the argument is infinite, then the result is 2²⁸.
• If the argument is zero, then the result is -(2²⁸).

Parameters:

d - floating-point number whose exponent is to be extracted

Returns:

unbiased exponent of the argument.

ilogb

public static int ilogb(float f)

Returns unbiased exponent of a float; for subnormal values, the number is treated as if it were normalized. That is for all finite, non-zero, positive numbers x, scalb(x, -ilogb(x)) is always in the range [1, 2).

Special cases:

• If the argument is NaN, then the result is 2³⁰.
• If the argument is infinite, then the result is 2²⁸.
• If the argument is zero, then the result is -(2²⁸).

Parameters:

f - floating-point number whose exponent is to be extracted

Returns:

unbiased exponent of the argument.

scalb

public static double scalb(double d,
                           int scale_factor)

Return d × 2^scale_factor rounded as if performed by a single correctly rounded floating-point multiply to a member of the double value set. See §4.2.3 of the Java Language Specification for a discussion of floating-point value sets. If the exponent of the result is between the double's minimum exponent and maximum exponent, the answer is calculated exactly. If the exponent of the result would be larger than doubles's maximum exponent, an infinity is returned. Note that if the result is subnormal, precision may be lost; that is, when scalb(x, n) is subnormal, scalb(scalb(x, n), -n) may not equal x. When the result is non-NaN, the result has the same sign as d.

Special cases:

• If the first argument is NaN, NaN is returned.
• If the first argument is infinite, then an infinity of the same sign is returned.
• If the first argument is zero, then a zero of the same sign is returned.

Parameters:

d - number to be scaled by a power of two.

scale_factor - power of 2 used to scale d

Returns:

d * 2^scale_factor

scalb

public static float scalb(float f,
                          int scale_factor)

Return f × 2^scale_factor rounded as if performed by a single correctly rounded floating-point multiply to a member of the float value set. See §4.2.3 of the Java Language Specification for a discussion of floating-point value set. If the exponent of the result is between the float's minimum exponent and maximum exponent, the answer is calculated exactly. If the exponent of the result would be larger than float's maximum exponent, an infinity is returned. Note that if the result is subnormal, precision may be lost; that is, when scalb(x, n) is subnormal, scalb(scalb(x, n), -n) may not equal x. When the result is non-NaN, the result has the same sign as f.

Special cases:

• If the first argument is NaN, NaN is returned.
• If the first argument is infinite, then an infinity of the same sign is returned.
• If the first argument is zero, then a zero of the same sign is returned.

Parameters:

f - number to be scaled by a power of two.

scale_factor - power of 2 used to scale f

Returns:

f * 2^scale_factor

nextAfter

public static double nextAfter(double start,
                               double direction)

Returns the floating-point number adjacent to the first argument in the direction of the second argument. If both arguments compare as equal the second argument is returned.

Special cases:

• If either argument is a NaN, then NaN is returned.
• If both arguments are signed zeros, direction is returned unchanged (as implied by the requirement of returning the second argument if the arguments compare as equal).
• If start is ±Double.MIN_VALUE and direction has a value such that the result should have a smaller magnitude, then a zero with the same sign as start is returned.
• If start is infinite and direction has a value such that the result should have a smaller magnitude, Double.MAX_VALUE with the same sign as start is returned.
• If start is equal to ± Double.MAX_VALUE and direction has a value such that the result should have a larger magnitude, an infinity with same sign as start is returned.

Parameters:

start - starting floating-point value

direction - value indicating which of start's neighbors or start should be returned

Returns:

The floating-point number adjacent to start in the direction of direction.

nextAfter

public static float nextAfter(float start,
                              double direction)

Returns the floating-point number adjacent to the first argument in the direction of the second argument. If both arguments compare as equal, the second argument is returned.

Special cases:

• If either argument is a NaN, then NaN is returned.
• If both arguments are signed zeros, a float zero with the same sign as direction is returned (as implied by the requirement of returning the second argument if the arguments compare as equal).
• If start is ±Float.MIN_VALUE and direction has a value such that the result should have a smaller magnitude, then a zero with the same sign as start is returned.
• If start is infinite and direction has a value such that the result should have a smaller magnitude, Float.MAX_VALUE with the same sign as start is returned.
• If start is equal to ± Float.MAX_VALUE and direction has a value such that the result should have a larger magnitude, an infinity with same sign as start is returned.

Parameters:

start - starting floating-point value

direction - value indicating which of start's neighbors or start should be returned

Returns:

The floating-point number adjacent to start in the direction of direction.

nextUp

public static double nextUp(double d)

Returns the floating-point value adjacent to d in the direction of positive infinity. This method is semantically equivalent to nextAfter(d, Double.POSITIVE_INFINITY); however, a nextUp implementation may run faster than its equivalent nextAfter call.

Special Cases:

• If the argument is NaN, the result is NaN.
• If the argument is positive infinity, the result is positive infinity.
• If the argument is zero, the result is Double.MIN_VALUE

Parameters:

d - starting floating-point value

Returns:

The adjacent floating-point value closer to positive infinity.

nextUp

public static float nextUp(float f)

Returns the floating-point value adjacent to f in the direction of positive infinity. This method is semantically equivalent to nextAfter(f, Double.POSITIVE_INFINITY); however, a nextUp implementation may run faster than its equivalent nextAfter call.

Special Cases:

• If the argument is NaN, the result is NaN.
• If the argument is positive infinity, the result is positive infinity.
• If the argument is zero, the result is Float.MIN_VALUE

Parameters:

f - starting floating-point value

Returns:

The adjacent floating-point value closer to positive infinity.

nextDown

public static double nextDown(double d)

Returns the floating-point value adjacent to d in the direction of negative infinity. This method is semantically equivalent to nextAfter(d, Double.NEGATIVE_INFINITY); however, a nextDown implementation may run faster than its equivalent nextAfter call.

Special Cases:

• If the argument is NaN, the result is NaN.
• If the argument is negative infinity, the result is negative infinity.
• If the argument is zero, the result is -Double.MIN_VALUE

Parameters:

d - starting floating-point value

Returns:

The adjacent floating-point value closer to negative infinity.

nextDown

public static double nextDown(float f)

Returns the floating-point value adjacent to f in the direction of negative infinity. This method is semantically equivalent to nextAfter(f, Float.NEGATIVE_INFINITY); however, a nextDown implementation may run faster than its equivalent nextAfter call.

Special Cases:

• If the argument is NaN, the result is NaN.
• If the argument is negative infinity, the result is negative infinity.
• If the argument is zero, the result is -Float.MIN_VALUE

Parameters:

f - starting floating-point value

Returns:

The adjacent floating-point value closer to negative infinity.

copySign

public static double copySign(double magnitude,
                              double sign)

Returns the first floating-point argument with the sign of the second floating-point argument. For this method, a NaN sign argument is always treated as if it were positive.

Parameters:

magnitude - the parameter providing the magnitude of the result

sign - the parameter providing the sign of the result

Returns:

a value with the magnitude of magnitude and the sign of sign.

Since:

1.5

copySign

public static float copySign(float magnitude,
                             float sign)

Returns the first floating-point argument with the sign of the second floating-point argument. For this method, a NaN sign argument is always treated as if it were positive.

Parameters:

magnitude - the parameter providing the magnitude of the result

sign - the parameter providing the sign of the result

Returns:

a value with the magnitude of magnitude and the sign of sign.

ulp

public static double ulp(double d)

Returns the size of an ulp of the argument. An ulp of a double value is the positive distance between this floating-point value and the double value next larger in magnitude. Note that for non-NaN x, ulp(-x) == ulp(x).

Special Cases:

• If the argument is NaN, then the result is NaN.
• If the argument is positive or negative infinity, then the result is positive infinity.
• If the argument is positive or negative zero, then the result is Double.MIN_VALUE.
• If the argument is ±Double.MAX_VALUE, then the result is equal to 2⁹⁷¹.

Parameters:

d - the floating-point value whose ulp is to be returned

Returns:

the size of an ulp of the argument

Since:

1.5

ulp

public static float ulp(float f)

Returns the size of an ulp of the argument. An ulp of a float value is the positive distance between this floating-point value and the float value next larger in magnitude. Note that for non-NaN x, ulp(-x) == ulp(x).

Special Cases:

• If the argument is NaN, then the result is NaN.
• If the argument is positive or negative infinity, then the result is positive infinity.
• If the argument is positive or negative zero, then the result is Float.MIN_VALUE.
• If the argument is ±Float.MAX_VALUE, then the result is equal to 2¹⁰⁴.

Parameters:

f - the floating-point value whose ulp is to be returned

Returns:

the size of an ulp of the argument

Since:

1.5

signum

public static double signum(double d)

Returns the signum function of the argument; zero if the argument is zero, 1.0 if the argument is greater than zero, -1.0 if the argument is less than zero.

Special Cases:

• If the argument is NaN, then the result is NaN.
• If the argument is positive zero or negative zero, then the result is the same as the argument.

Parameters:

d - the floating-point value whose signum is to be returned

Returns:

the signum function of the argument

Since:

1.5

signum

public static float signum(float f)

Returns the signum function of the argument; zero if the argument is zero, 1.0f if the argument is greater than zero, -1.0f if the argument is less than zero.

Special Cases:

• If the argument is NaN, then the result is NaN.
• If the argument is positive zero or negative zero, then the result is the same as the argument.

Parameters:

f - the floating-point value whose signum is to be returned

Returns:

the signum function of the argument

Since:

1.5